Over the last year, I've been spending as much free time as I can working on a mobile membership application for a start-up gym in my area. The application is nearly complete, but as I've been working on it, I've started envisioning better ways for the gym to run their business to involve their members more, as well as to improve their business process. Allow me to explain:

They currently keep member records in a paper file,which is time consuming to look up who's paid membership fees, what classes they've signed up for, etc. They handle billing for credit cards through a 3rd party vendor, so that's another record system they have to keep track of. They then handle signups and check-ins using another system, so that's three, and last but not least, there's the new mobile app, which uses a MySQL database on a web-server, so if you're keeping track, we have four record systems now.

What I envisioned for them was some sort of site, probably in PHP, that provided all these functions in one, namely:

Admin page for the owners/instructors to add new members, keep track of billing, registration details, etc

User portal for the members to log in, see their account, renew membership, see their progress in classes, etc.

Mobile API to have the mobile apps tie in.

I've designed the mobile app to point to a MySQL database through a PHP api. Ideally the app would be able to pull/write data to the same database used by the admin portal/user portal, so that if they logged an activity on the app, they could then see their progress on the site.

I don't think anything exists like this, so it would probably require hiring a developer, but I don't know what it would cost do do something like this, or if there are similar systems that exist already? If so, can anyone recommend some starting examples to go look at, or if you think this is doable, do you have any idea what it would cost to create something like this?